Wiper control method and wiper control device

ABSTRACT

An electric motor is subjected to PWM duty control based on a target speed (tgt spd) set according to a position of a wiper blade. After a deceleration start position of wiping operation, the electric motor is driven at a PWM duty value (sld sta duty×Ksd) obtained by multiplying a PWM duty value (sld sta duty) at the deceleration start position by a predetermined deceleration coefficient (Ksd) set according to the blade position. The deceleration coefficient (Ksd) is set according to the position of the wiper blade based on a ratio (tgt spd/pek tgt spd) between the target speed (pek tgt spd) of the wiper blade at the start of deceleration and the target speed (tgt spd) of the wiper blade.

TECHNICAL FIELD

The present invention relates to control technology of a vehicle wiperdevice mounted on a vehicle or the like and, more particularly, tostabilization of wiping movement near an inversion position.

BACKGROUND ART

There has been widely used a system that detects a current position of awiper blade on a glass surface and makes the wiper blade performreciprocating wiping operation between an upper inversion position and alower inversion position based on the detection data. As a control modein such a wiper system, there is known a method that uses an elapsedtime from an inversion position, angle information of a motor shaft, acount number of pulses output with motor rotation, and the like(hereinafter, abbreviated as “elapsed time, etc.”) to detect a bladeposition and controls a wiper motor based on the detected bladeposition. In this method, for example, the elapsed time, etc., and theblade position (angle) are previously associated with each other and,thereby, a current position of the blade is detected based on theelapsed time, etc. Then, a target speed is set based on the detectedblade position, and a motor is feedback-controlled according to the settarget speed, whereby the wiper blade is reciprocated at a predeterminedwiping cycle.

CITATION LIST Patent Document

[Patent Document 1] Jpn. Pat. Appln. Laid-Open Publication No.2002-264776

[Patent Document 2] Jpn. Pat. Appln. Laid-Open Publication No.2010-173338

SUMMARY OF THE INVENTION

However, in the wiper device, when the wiper blade passes through near avertical direction center portion of a glass surface in a backwardwiping stroke (from upper inversion position to lower inversionposition), a load is abruptly reduced by a gravity component applied tothe wiper blade. When the load is abruptly reduced, a blade speed duringcontrol exceeds a target speed. Thus, when a PI feedback control isperformed at that time, a PWM Duty of a motor is reduced so as to reducethe speed. Then, the speed falls below the target speed, and the PWMDuty is increased so as to increase the speed. This repetition causes adisturbance in the PWM duty, a motor rotation number, and a pivot shaftrotating speed (blade speed) as indicated by dashed circles in FIG. 10,which may result in control instability (counter state). This may inturn cause so-called a stick-slip movement in which the wiper bladeunexpectedly stops or suddenly starts to move in a boundary regionbetween a dynamic friction state and a static friction state.

Also in a forward wiping stroke (from lower inversion position to upperinversion position), when the blade approaches the upper inversionposition, the load is abruptly reduced, and this may result in controlinstability. For example, when a vehicle speed exceeds a certain valuewhile the vehicle is traveling, a relationship between a gravitycomponent applied to the blade and the like and an external forcecomponent caused by vehicle traveling wind may be reversed. When such aphenomenon occurs, the same phenomenon as that occurs in the backwardwiping operation may occur also in the forward wiping operation, whichmay make movement of the wiper blade unstable.

A wiper control method according to an aspect of the present inventionis a control method for a wiper device, the wiper device including awiper blade disposed on a surface to be wiped and an electric motor forreciprocating the wiper blade on the surface to be wiped, the electricmotor being subjected to PWM duty control based on a target speed of thewiper blade set according to a position of the wiper blade on thesurface to be wiped, the method being characterized in that after adeceleration start position at which a speed of the wiper blade is madeto start being reduced in a wiping operation of the wiper blade, theelectric motor is driven using a PWM duty value (sld sta duty×Ksd)obtained by multiplying a PWM duty value (sld sta duty) at thedeceleration start position by a predetermined deceleration coefficientKsd set according to the position of the wiper blade on the surface tobe wiped.

A wiper control method according to another aspect of the presentinvention is a control method for a wiper device, the wiper deviceincluding a wiper blade disposed on a surface to be wiped and anelectric motor for reciprocating the wiper blade on the surface to bewiped, the electric motor being subjected to PWM duty control based on atarget speed of the wiper blade set according to a position of the wiperblade on the surface to be wiped, the method being characterized in thatafter a deceleration start position at which a speed of the wiper bladeis made to start being reduced in a wiping operation of the wiper blade,the electric motor is driven using a PWM duty value (ffc sta duty×Ksd)obtained by multiplying a PWM duty value (ffc sta duty) at a feedforwardcontrol start position set before the deceleration start position by apredetermined deceleration coefficient Ksd set according to the positionof the wiper blade on the surface to be wiped.

In the above inventions, after the deceleration start position, theelectric motor is driven by the PWM duty value obtained by multiplyingthe PWM duty value at the deceleration start position or PWM duty valueat the feedforward control start position set before the decelerationstart position by the predetermined deceleration coefficient Ksd, sothat, after the deceleration start position, the blade speed iscontrolled by a predetermined value. Thus, even in a vehicle having alarge load fluctuation, it is possible to suppress disturbance in theduty or motor rotation number due to an abrupt change in the load,thereby suppressing abnormal movement of the blade, such as stick-slip,which allows stabilization of the wiping movement.

In the wiper control method, the deceleration coefficient Ksd may be setbased on a ratio (tgt spd/pek tgt spd) between the target speed pek tgtspd at the deceleration start point and target speed tgt spd setaccording to the position of the wiper blade.

Further, wiper control may be performed such that the electric motor isfeedback-controlled based on the speed of the wiper blade and is, afterthe deceleration start position, not subjected to the feedback controlbut driven using only the value obtained by multiplying the PWM dutyvalue (sld sta duty) at the deceleration start position by thedeceleration coefficient Ksd or value obtained by multiplying the PWMduty value (ffc sta duty) at the feedforward control start position setbefore the deceleration start position by the deceleration coefficientKsd.

Further, wiper control may be performed such that after the decelerationstart position, the electric motor is not subjected to the feedbackcontrol based on the speed of the wiper blade but is driven undercoefficient control using the value obtained by multiplying the PWM dutyvalue (sld sta duty) at the deceleration start position by thedeceleration coefficient Ksd or value obtained by multiplying the PWMduty value (ffc sta duty) at the feedforward control start position setbefore the deceleration start position by the deceleration coefficientKsd and is driven under the feedback control in place of the coefficientcontrol when the speed of the wiper blade deviates from the target speedby a predetermined value or more.

Further, wiper control may be performed such that the electric motor isfeedback-controlled based on the speed of the wiper blade and is, afterthe deceleration start position, driven by combination of the feedbackcontrol and control using the value obtained by multiplying the PWM dutyvalue (sld sta duty) at the deceleration start position by thedeceleration coefficient Ksd or value obtained by multiplying the PWMduty value (ffc sta duty) at the feedforward control start position setbefore the deceleration start position by the deceleration coefficientKsd. In this case, after the deceleration start position, the electricmotor may be driven by an output PWM duty value:output PWM duty=(a×D1+b×D2)/c(where, c=a+b) oroutput PWM duty=(a×D _(ff) +b×D _(fb))/c(where, c=a+b)calculated using a value D1 obtained by multiplying the PWM duty value(sld sta duty) at the deceleration start position by the decelerationcoefficient Ksd or value D_(ff) obtained by multiplying the PWM dutyvalue (ffc sta duty) at the feedforward control start position setbefore the deceleration start position by the deceleration coefficientKsd and a PWM duty value D2 (D_(fb)) based on the feedback control.

A wiper control method according to still another aspect of the presentinvention is a control method for a wiper device, the wiper deviceincluding a wiper blade disposed on a surface to be wiped and anelectric motor for reciprocating the wiper blade on the surface to bewiped, the electric motor being subjected to PWM duty control based on atarget speed of the wiper blade set according to a position of the wiperblade on the surface to be wiped, the method being characterized in thatthe wiper device has, in one control cycle of the wiper blade, adeceleration region over which the electric motor is decelerated, and inthe deceleration region, the electric motor is driven under apredetermined control mode set according to a load state in a regionover which the wiper blade on the surface to be wiped is operating at amaximum speed. With this configuration, after the deceleration startposition, blade speed control is performed according to the load statein the maximum speed region, allowing stabilization of the wipingmovement of the blade.

A control device according to an aspect of the present invention is acontrol device for a wiper device, the wiper device including a wiperblade disposed on a surface to be wiped and an electric motor forreciprocating the wiper blade on the surface to be wiped, the electricmotor being subjected to PWM duty control based on a target speed of thewiper blade set according to a position of the wiper blade on thesurface to be wiped, the control device comprising: a blade positiondetection section that detects a current position of the wiper blade; ablade speed detection section that detects a current moving speed of thewiper blade; a blade speed determination section that compares a bladetarget speed tgt spd corresponding to the current position of the wiperblade and the current speed of the wiper blade; a motor rotation numbercalculation section that calculates a rotation number of the electricmotor based on a result of the determination made by the blade speeddetermination section; and a drive control instruction section thatcontrols operation of the electric motor based on an instruction fromthe motor rotation number calculation section, wherein after adeceleration start position at which a speed of the wiper blade is madeto start being reduced in a wiping operation of the wiper blade, themotor rotation number calculation section uses, as a PWM duty value forthe electric motor, a value (sld sta duty×Ksd) obtained by multiplying aPWM duty value (sld sta duty) at the deceleration start position by apredetermined deceleration coefficient Ksd set according to the positionof the wiper blade on the surface to be wiped.

Further, a control device according to another aspect of the presentinvention is a control device for a wiper device, the wiper deviceincluding a wiper blade disposed on a surface to be wiped and anelectric motor for reciprocating the wiper blade on the surface to bewiped, the electric motor being subjected to PWM duty control based on atarget speed of the wiper blade set according to a position of the wiperblade on the surface to be wiped, the control device comprising: a bladeposition detection section that detects a current position of the wiperblade; a blade speed detection section that detects a current movingspeed of the wiper blade; a blade speed determination section thatcompares a blade target speed tgt spd corresponding to the currentposition of the wiper blade and the current speed of the wiper blade; amotor rotation number calculation section that calculates a rotationnumber of the electric motor based on a result of the determination madeby the blade speed determination section; and a drive controlinstruction section that controls operation of the electric motor basedon an instruction from the motor rotation number calculation section,wherein after a deceleration start position at which a speed of thewiper blade is made to start being reduced in a wiping operation of thewiper blade, the motor rotation number calculation section uses a PWMduty value (ffc sta duty×Ksd) obtained by multiplying a PWM duty value(ffc sta duty) at a feedforward control start position set before thedeceleration start position by a predetermined deceleration coefficientKsd set according to the position of the wiper blade on the surface tobe wiped.

In the above inventions, there are provided the blade speeddetermination section that compares the blade target speed tgt spdcorresponding to the current position of the wiper blade and the currentspeed of the wiper blade and motor rotation number calculation sectionthat calculates a rotation number of the electric motor based on aresult of the determination made by the blade speed determinationsection. After the deceleration start position, the motor rotationnumber calculation section uses, as the PWM duty value, the PWM dutyvalue obtained by multiplying the PWM duty value (sld sta duty) at thedeceleration start position or PWM value at the feedforward controlstart position set before the deceleration start position by thepredetermined deceleration coefficient Ksd to drive the electric motor,so that, after the deceleration start position, the blade speed iscontrolled by a predetermined value. Thus, even in a vehicle having alarge load fluctuation, it is possible to suppress disturbance in theduty or motor rotation number due to an abrupt change in the load,thereby suppressing abnormal movement of the blade, such as stick-slip,which allows stabilization of the wiping movement.

In the wiper control device, the deceleration coefficient Ksd may be setbased on a ratio (tgt spd/pek tgt spd) between the target speed pek tgtspd at the deceleration start point and target speed tgt spd setaccording to the position of the wiper blade.

Further, wiper control may be performed such that the electric motor isfeedback-controlled by the motor rotation number calculation sectionbased on the speed of the wiper blade and is, after the decelerationstart position, not subjected to the feedback control but driven usingonly the value obtained by multiplying the PWM duty value (sld sta duty)at the deceleration start position by the deceleration coefficient Ksdor value obtained by multiplying the PWM duty value (ffc sta duty) atthe feedforward control start position set before the deceleration startposition by the predetermined deceleration coefficient Ksd.

Further, wiper control may be performed such that after the decelerationstart position, the electric motor is not subjected to the feedbackcontrol by the motor rotation number calculation section but is drivenunder coefficient control using the value obtained by multiplying thePWM duty value (sld sta duty) at the deceleration start position by thedeceleration coefficient Ksd or value obtained by multiplying the PWMduty value (ffc sta duty) at the feedforward control start position setbefore the deceleration start position by the predetermined decelerationcoefficient Ksd and is driven under the feedback control in place of thecoefficient control when the speed of the wiper blade deviates from thetarget speed by a predetermined value or more.

Further, wiper control may be performed such that the electric motor isfeedback-controlled by the motor rotation number calculation sectionbased on the speed of the wiper blade and is, after the decelerationstart position, driven by combination of the feedback control andcontrol using the value obtained by multiplying the PWM duty value (sldsta duty) at the deceleration start position by the decelerationcoefficient Ksd or value obtained by multiplying the PWM duty value (ffcsta duty) at the feedforward control start position set before thedeceleration start position by the deceleration coefficient Ksd. In thiscase, after the deceleration start position, the electric motor may bedriven by an output PWM duty value:output PWM duty=(a×D1+b×D2)/c(where, c=a+b) oroutput PWM duty=(a×D _(ff) +b×D _(fb))/c(where, c=a+b)calculated using a value D1 obtained by multiplying the PWM duty value(sld sta duty) at the deceleration start position by the decelerationcoefficient Ksd or value D_(ff) obtained by multiplying the PWM dutyvalue (ffc sta duty) at the feedforward control start position setbefore the deceleration start position by the deceleration coefficientKsd and a PWM duty value D2 (D_(fb)) based on the feedback control.

Further, a control device according to still another aspect of thepresent invention is a control device for a wiper device, the wiperdevice including a wiper blade disposed on a surface to be wiped and anelectric motor for reciprocating the wiper blade on the surface to bewiped, the electric motor being subjected to PWM duty control based on atarget speed of the wiper blade set according to a position of the wiperblade on the surface to be wiped, the control device being characterizedin that the wiper device has, in one control cycle of the wiper blade, adeceleration region over which the electric motor is decelerated, and inthe deceleration region, the control device drives the electric motorunder a predetermined control mode set according to a load state in aregion over which the wiper blade on the surface to be wiped isoperating at a maximum speed. With this configuration, after thedeceleration start position, blade speed control is performed accordingto the load state in the maximum speed region, allowing stabilization ofthe wiping movement of the blade.

According to the wiper control method of the present invention, afterthe deceleration start position of the wiper blade wiping operation, theelectric motor is driven using the PWM duty value obtained bymultiplying the PWM duty value at the deceleration start position or PWMduty value at the feedforward control start position set before thedeceleration start position by the predetermined decelerationcoefficient Ksd, so that, after the deceleration start position, theblade speed is controlled based on a predetermined value. Thus, it ispossible to suppress disturbance in the duty or motor rotation numberdue to an abrupt change in the load, thereby suppressing abnormalmovement of the blade, such as stick-slip, which may occur after thedeceleration start position, which allows stabilization of the wipingmovement.

According to the wiper device of the present invention, there areprovided the blade speed determination section that compares the bladetarget speed corresponding to the current position of the wiper bladeand the current speed of the wiper blade and motor rotation numbercalculation section that calculates a rotation number of the electricmotor based on a result of the determination made by the blade speeddetermination section. After the deceleration start position of thewiper blade wiping operation, the motor rotation number calculationsection uses the PWM duty value obtained by multiplying the PWM dutyvalue at the deceleration start position or PWM value at the feedforwardcontrol start position set before the deceleration start position by thepredetermined deceleration coefficient Ksd to drive the electric motor,so that, after the deceleration start position, the blade speed iscontrolled by a predetermined value. Thus, it is possible to suppressdisturbance in the duty or motor rotation number due to an abrupt changein the load, thereby suppressing abnormal movement of the blade, such asstick-slip, which may occur after the deceleration start position, whichallows stabilization of the wiping movement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view illustrating an entire configuration of awiper system driven by a control method/control device according to afirst embodiment of the present invention.

FIG. 2 is an explanatory view illustrating a configuration of anelectric motor used in the wiper system of FIG. 1.

FIG. 3 is a block diagram illustrating a configuration of a controlsystem of a wiper control device according to the present invention.

FIG. 4 is a flowchart illustrating a processing procedure of a wipercontrol method according to the present invention.

FIG. 5 is an explanatory view illustrating temporal changes in a PWMduty, a blade speed, and a motor rotation number in the wiper systemaccording to the present invention.

FIGS. 6A and 6B are each an explanatory view explanatory viewillustrating temporal changes in the PWM duty, blade speed, and motorrotation number when water is sprayed near the lower inversion positionin the backward wiping stroke, in which FIG. 6A illustrates a case wherethe control according to a second embodiment is performed, and FIG. 6Billustrates a case where the control according to the first embodimentis performed.

FIG. 7 is an explanatory view illustrating control processing to beperformed in a control mode according to a third embodiment.

FIG. 8 is a flowchart illustrating a processing procedure of the wipercontrol method according to the third embodiment.

FIG. 9 is an explanatory view illustrating concepts of a FF controlstart position P, and a current target speed tgt spd and a target speedpek tgt spd at the deceleration start point in the present invention.

FIG. 10 is an explanatory view illustrating temporal changes in the PWMduty, blade speed, and motor rotation number in a conventional controlsystem.

Now, embodiments of the present invention will be described in greaterdetail by referring to the drawings. An object of the followingembodiments is to suppress disturbance of control due to fluctuation ina blade load and stabilize wiping movement of a wiper blade near aninversion position in a vehicle wiper device.

FIRST EMBODIMENT

FIG. 1 is an explanatory view illustrating an entire configuration of awiper system driven by a control method/control device according to afirst embodiment of the present invention. A wiper device of FIG. 1includes a driver's seat side wiper arm 1 a and a passenger's seat sidewiper arm 1 b. The wiper arms 1 a and 1 b are swingably attached to avehicle body. A driver's seat side wiper blade 2 a and a passenger'sseat side wiper blade 2 b are connected to the wiper arms 1 a and 1 b,respectively. The wiper blades 2 a and 2 b (hereinafter, abbreviated as“blades 2 a and 2 b”) are brought into elastic contact with a windshield3 by a not illustrated spring member provided inside the wiper arms 1 aand 1 b. Two wiper shafts (pivot shafts) 4 a and 4 b are fixed to thevehicle body. Base end portions of the wiper arms 1 a and 1 b are fixedto the wiper shafts 4 a and 4 b, respectively. The “a, b” of thereference numeral indicates that components or portions are provided onboth the driver's seat side and passenger's seat side.

The wiper system has two electric motors 6 a and 6 b (hereinafter,abbreviated as “motors 6 a and 6 b”) for swinging the wiper arms 1 a and1 b. The motors 6 a and 6 b are each constituted by a motor body 7 and adeceleration mechanism 8. The motors 6 a and 6 b are subjected to PWMduty control by wiper control devices 10 a and 10 b, respectively, to berotated in forward and backward directions. The wiper control device 10a controlling drive of the motor 6 a is connected to an ECU 11 as avehicle side control device through an on-vehicle LAN 12. Switchinformation such as ON/OFF, Lo, Hi, INT (intermittent operation) or thelike of a wiper switch, engine start-up information, and the like areinput from the ECU 11 to the wiper control device 10 a through the LAN12. The wiper control devices 10 a and 10 b are connected to each otherthrough a communication line 13.

In the wiper system of FIG. 1, the motors 6 a and 6 b arefeedback-controlled (PI-controlled) based on position information of theblades 2 a and 2 b, respectively. In this example, target speeds tgt spdof both the blades are set according to the positions of the respectiveblades 2 a and 2 b. The target speeds tgt spd are previously stored inthe respective wiper control devices 10 a and 10 b in the form of a mapor the like. The wiper control devices 10 a and 10 b detect currentpositions of the respective blades 2 a and 2 b and detects moving speedsof the respective blades 2 a and 2 b from rotating speeds of therespective wiper shafts 4 a and 4 b. The control devices 10 a and 10 bcompares the current speeds of the blades 2 a and 2 b with the targetspeeds tgt spd of the blades 2 a and 2 b at positions where the currentspeeds are detected and appropriately controls each of the motors 6 aand 6 b according to a difference between the target speed tgt spd andcurrent speed.

For feedback control, the motors 6 a and 6 b each have a sensor magnet31 and a rotary encoder IC 32. FIG. 2 is an explanatory viewillustrating a configuration of the motor 6 a. The motor 6 b has thesame configuration as that of the motor 6 a. As described above, themotor 6 a is constituted by the motor body 7 and deceleration mechanism8. A rotor 33 is rotatably disposed inside the motor body 7. A worm 35is fixed to a rotary shaft 34 of the rotor 33. The worm 35 is engagedwith a worm wheel 36 disposed in the deceleration mechanism 8. The wormwheel 36 is fixed to the wiper shaft 4 a. The sensor magnet 31 isattached to the wiper shaft 4 a or worm wheel 36. A not illustratedcontrol board is provided on the deceleration mechanism 8 side of themotor 6 a. The sensor magnet 31 is disposed so as to face the rotaryencoder IC 32 mounted to the control board.

The rotary encoder IC 32 converts a change in an output voltage due to achange in magnetism of the sensor magnet 31 into an angle to therebydetect a rotation angle of the wiper shaft 4 a. There is a predeterminedrelationship between an output voltage value of the rotary encoder IC 32and the rotation angle of the wiper shaft 4 a, and the current positionof the blade 2 a is detected based on the output voltage value. Further,the rotating speed of the wiper shaft 4 a is calculated by detecting anangle change of the wiper shaft 4 a per unit time, whereby the speed ofthe blade 2 a is detected. A method for calculating the rotation angleand rotating speed of the wiper shaft 4 a is not limited to a methodusing the above rotary encoder IC 32, but may be one based on pulsedetection using a hall IC.

Control information such as the speed and current position of the blade2 a is exchanged between the wiper control devices 10 a and 10 b throughthe communication line 13. The wiper control devices 10 a and 10 bsynchronously control the motors 6 a and 6 b based on the positionalrelationship between the blades. That is, the wiper control devices 10 aand 10 b control forward/backward rotation of the motors 6 a and 6 b,respectively, based on the positions of their corresponding blades and,at the same time, control the motors 6 a and 6 b based on the positioninformation of the blades 2 a and 2 b to thereby control the wipersystem so as not to cause interference between the blades or not toincrease a difference in angle between the blades. As a result, theblades 2 a and 2 b are each brought into swing movement between a lowerinversion position A and an upper inversion position B, i.e., within awiping range 5 indicated by a long dashed short dashed line in FIG. 1,whereby rain or snow adhered to the windshield 3 is wiped awaytherefrom.

Also in the wiper system of FIG. 1, when the blades 2 a and 2 b eachpass through a vertical direction center portion of the windshield 3 andreach a lower half region thereof in the backward wiping stroke, theload is abruptly reduced. This may cause a disturbance in the PWM dutyor motor rotation number, as described above. Thus, in the wiper systemaccording to the present embodiment, in order to prevent control frombeing unstable due to abrupt fluctuation in the load, a Duty calculationmethod is changed after a deceleration start position in the backwardwiping stroke to thereby suppress output fluctuation of the motors 6 aand 6 b due to disturbance. FIG. 3 is a block diagram illustrating aconfiguration of a control system of the wiper control device 10according to the present invention. FIG. 4 is a flowchart illustrating aprocessing procedure of the wiper control method according to thepresent invention. Processing of FIG. 4 are executed by the wipercontrol devices 10 a and 10 b. The wiper control devices 10 a and 10 bhave the same configuration, so only a configuration of the wipercontrol device 10 a will be described in FIG. 3 and in the followingdescription.

As illustrated in FIG. 3, a CPU 21 and a data transmission/receptionsection 22 are provided in the wiper control device 10 a. The wipercontrol device 10 a is connected to the ECU 11 through the LAN 12. Thewiper control device 10 a receives, from the ECU 11, input of variousvehicle information such as a wiper switch setting state (operation modesetting such as ON/OFF, Lo, Hi, or INT) or an engine start-up signal).Further, a ROM 23 and a RAM 24 are provided in the wiper control device10 a. The ROM 23 stores a control program and various controlinformation. The RAM 24 stores data necessary for control, such as amotor rotation number and blade current position.

The CPU 21 is a central processing unit. In the present embodiment, theCPU connected to the ECU 11 serves as a master and a not illustrated CPUof the wiper control device 10 b serves as a slave. The CPU 21 of thewiper control device 10 a is connected to the CPU of the wiper controldevice 10 b through the data transmission/reception section 22 andcommunication line 13. Both the CPUs exchange positional information oran operation instruction through the communication line 13. Themaster-side CPU 21 controls operation of the motor 6 a based on theposition information of the blade 2 b received from the wiper controldevice 10 b and position information of the blade 2 a detected by itselfaccording to a state of the wiper switch. The slave-side CPU controlsoperation of the motor 6 b based on the position information of theblade 2 a received from the wiper control device 10 a and positioninformation of the blade 2 b detected by itself according to aninstruction from the wiper control device 10 a.

The CPU 21 further includes a position detection section 25, a bladespeed detection section 26, a blade speed determination section 27, amotor rotation number calculation section 28, and a drive controlinstruction section 29. The position detection section 25 detects acurrent position of the blade 2 a based on a sensor signal from therotary encoder IC 32. The blade speed detection section 26 detects acurrent moving speed of the blade 2 a. The blade speed determinationsection 27 reads a blade target speed tgt spd from the ROM 23corresponding to the current position of the blade 2 a and compares theblade target speed tgt spd and current speed of the blade 2 a.

The motor rotation number calculation section 28 calculates a rotationnumber of the motor 6 a based on a result of the determination made bythe blade speed determination section 27, a positional relationship withthe other blade, wiper switch information, and the like. The drivecontrol instruction section 29 gives a rotation direction, Duty, and thelike to the motor 6 a based on an instruction from the motor rotationnumber calculation section 28 and appropriately moves the blade 2 abetween the upper and lower inversion positions. The motor rotationnumber calculation section 28 determines the rotation number of themotor 6 a considering the above-mentioned conditions. However, in thewiper system according to the present invention, the Duty calculationmethod in the backward wiping stroke is changed at a deceleration startpoint to thereby suppress a rough change (irregular fluctuation) of themotor rotation number. The deceleration start point is not necessarily acenter of the backward wiping stroke. In the present embodiment, thedeceleration start point (position) refers to a time point (position) atwhich the motor starts deceleration after the blade 2 a passes a region(maximum speed region) over which it is operating at the maximum speedafter completion of acceleration.

In the wiper system according to the present invention, the followingprocessing is performed for the wiping operation. As illustrated in FIG.4, the current position of the blade 2 a is detected in step S1, and thecurrent speed of the blade 2 a is detected in step S2. The order ofsteps S1 and S2 may be reversed. After the current position and currentspeed of the blade 2 a are grasped in steps S1 and S2, the processingflow proceeds to step S3. In step S3, it is determined whether or notthe blade 2 a reaches a deceleration start position X in the backwardwiping stroke. As described above, the deceleration start position X isnot located at the center of the backward wiping stroke. When the blade2 a does not reach the deceleration start position X, the processingflow proceeds to step S4, where a target speed tgt spd corresponding tothe current position of the blade 2 a is acquired. The target speed tgtspd is stored in the ROM 23 as described above and is previously setwith the position of the blade 2 a as a parameter. By the processing ofstep S4, a target value of the blade speed corresponding to the currentposition of the blade 2 a is set.

After acquisition of the target speed tgt spd, the processing flowproceeds to step S5. In step S5, the motor rotation number calculationsection 28 determines current states (behind the set target?, ahead ofthe set target?, relationship between the blades is normal?, or thelike) of the blade from the positions of both blades. After that, theprocessing flow proceeds to step S6, where an optimum PWM duty value(control duty value) for the blade 2 a is set. The control duty value isset based on the current states of the blades and current speed andtarget speed tgt spd of the blade 2 a. Setting processing of thiscontrol duty value is also executed by the motor rotation numbercalculation section 28. After setting of the duty value, the processingflow proceeds to step S7, where the drive control instruction section 29outputs the PWM duty value based on the above setting value. As aresult, the motor 6 a is feedback-controlled based on the positions,speeds, and the like of the both blades, and this routine is ended.

On the other hand, when the blade 2 a reaches the deceleration startposition X in step S3, the processing flow proceeds to step S8, wherethe duty setting is changed. In this system, the motor rotation numbercalculation section 28 sets the PWM duty based on the followingexpression (expression (1)).Output PWM duty (D1)=PWM duty (sld sta duty) at deceleration startpoint×Ksd  (expression 1)(Ksd=current target speed tgt spd/target speed pek tgt spd atdeceleration start point)

Ksd is a control coefficient indicating a decrement in an output fromthe deceleration start point and is set according to the position of theblade 2 a. In this system, the control coefficient Ksd is a ratiobetween the target speeds, i.e., a ratio between the target speed pektgt spd at the deceleration start position X and target speed tgt spd ofthe blade 2 a set according to the position of the wiper blade 2 a. Thecontrol coefficient Ksd is stored in the ROM 23 as a map correspondingto the blade position. The motor rotation number calculation section 28uses this map to set the output PWM duty based on the blade position.

After setting of the output PWM duty in step S8, the processing flowproceeds to step S7. In step S7, the drive control instruction section29 outputs the PWM duty value set based on the expression (1). As aresult, the motor 6 a is driven based on a predetermined value (valuecalculated by expression (1)) described in the map after thedeceleration start position X without feedback control.

FIG. 5 is an explanatory view illustrating temporal changes in the PWMduty, blade speed, and motor rotation number in the wiper system. Asdescribed above, the duty after the deceleration start is set to a valueobtained by multiplying the duty (sld sta duty: slow down start duty) atthe deceleration start point by the ratio of the current target speedtgt spd (target speed) to the target speed pek tgt spd (peak targetspeed) at the deceleration start point (expression (1)). Consequently,as illustrated in FIG. 5, in the system according to the presentinvention, the output duty is reduced in a predetermined parabolic curveafter the deceleration start position, and the curve itself goes up anddown (duty value increases or decreases) according to the duty value (aload state in a maximum speed region) at the deceleration start point.That is, when the load is high in the maximum speed region, the duty isreduced as represented by a curve H in FIG. 5; when the load is low, theduty is reduced as represented by a curve L. Thus, in the decelerationregion, the motor 6 a is driven by a predetermined control mode setaccording to the load state in the maximum speed region.

In the wiper system according to the present invention, after thedeceleration start position in the backward wiping stroke, the PWM dutyvalue for motor drive is set based on the expression (1). Consequently,as illustrated in FIG. 5, after the deceleration start position, theblade speed and motor rotation number change in a parabolic fashionwithout disturbance while following the target value, with the resultthat they reach the lower inversion position in a smooth decelerationcurve. Thus, the disturbance in the duty or motor rotation number due toan abrupt change in the load, which is as illustrated in FIG. 10, can besuppressed, thereby suppressing abnormal movement of the blade, such asstick-slip, which allows stabilization of the wiping movement.

SECOND EMBODIMENT

The following describes, as a second embodiment of the presentinvention, a control mode in which a PI feedback control is performed inparallel also after the deceleration start position X. As describedabove, in the control mode according to the first embodiment, adverseaffect due to the abrupt reduction in the load can be properly avoided.However, when a state of the glass surface is abruptly changed from DRYto WET after the deceleration start position, the blade speed may becomeexcessive (overshoot). Thus, in the control mode of the secondembodiment, a PI feedback control is performed in parallel to thecontrol based on the expression (1) so as to improve correspondence tothe load fluctuation.

In the control according to the second embodiment, the processing ofstep S8 is changed as follows. That is, a duty value D1 is calculatedbased on the above expression (1), and a control duty value D2 in thefeedback control performed in steps S4 to S6 is calculated. Then, basedon these values D1, D2 and the following expression (2), the PWM dutyvalue is set/output.Output PWM duty=(a×D1+b×D2)/c  expression (2)(where, c=a+b)

That is, in determining the PWM duty value, both the specified value D1and feedback calculation value D2 are used, and weighting of the valuesD1 and D2 is appropriately adjusted, so as to properly cope with theabrupt reduction in the load and state change of the glass surface.

FIGS. 6A and 6B are each an explanatory view illustrating temporalchanges in the PWM duty, blade speed, and motor rotation number whenwater is sprayed near the lower inversion position in the backwardwiping stroke. FIG. 6A illustrates a case where the control according tothe second embodiment is performed, and FIG. 6B illustrates a case wherethe control according to the first embodiment is performed. In thecontrol mode of FIG. 6A, D1 and D2 are equivalently handled (a=1, b=1)in the expression (2), and D1 and D2 are added and then divided by two(c=2) (50% deceleration guidance). As illustrated in FIG. 6B, in thecontrol mode according to the first embodiment, when the glass surfaceis abruptly turned in a WET state after the deceleration start positionin the backward wiping stroke, it is impossible to cope with the WETstate since the feedback control is not performed, with the result thatthe blade speed abruptly increases (“water-sprayed portion” in a centerof FIG. 6B).

On the other hand, in the control mode according to the secondembodiment, although the blade speed increases due to the WET state, asituation in which the blade speed increases is properly grasped by thePI feedback control and reflected in the control. As a result, as shownin FIG. 6A, the speed increase is suppressed to allow disturbance in thespeed can be reduced to a low level (“water-sprayed portion” in a centerof FIG. 6A). As described above, in the control mode according to thesecond embodiment, control by the specified value D1 and PI feedbackcontrol are performed in parallel, whereby it is possible to reducedisturbance in the Duty or motor rotation number due to the load changewhile coping with the abrupt change in the glass surface state. Thus,adaptability to the disturbance is improved to allow the wiping movementto be further stabilized.

THIRD EMBODIMENT

The following describes, as a third embodiment of the present invention,a control mode in which a feedforward control (hereinafter abbreviatedas “FF control”) start position P is set at a position (e.g., a positionshifted by 10° from the deceleration start position X) short of thedeceleration start position X, and the duty value D1 is calculated basedon a PWM duty (ffc sta duty) at a FF control start point. FIG. 7 is anexplanatory view illustrating control processing to be performed in thecontrol mode according to the third embodiment, and FIG. 8 is aflowchart illustrating a processing procedure of the control processing.The FF control start position P is set within the above-mentionedmaximum speed region.

As illustrated in FIG. 7, in the wiper system of the third embodiment,the PI feedback control and FF control assuming disturbance are executedaccording to a processing procedure as illustrated in FIG. 8. Also inthis case, as illustrated in FIG. 8, the current position and currentspeed of the blade 2 a are detected in steps S11 and S12, respectively.Then, after the current position and current speed are grasped, theprocessing flow proceeds to step S13, where it is determined whether ornot the blade 2 a reaches the FF control start position P. When theblade 2 a does not reach the FF control start position P in step S13,the processing flow proceeds to steps S14 to S17. In steps S14 to S17,the PWM duty value is output based on the current states of the blades,and current speed and target speed tgt spd of the blade 2 a, as in stepsS4 to S7 of FIG. 4.

On the other hand, when the blade 2 a reaches the FF control startposition P in step S13, the processing flow proceeds to step S18. Instep S18, for the FF control, the current PWM duty (ffc sta duty) isacquired. After acquisition of the PWM duty (ffc sta duty), an FFcontrol start flag is set (FF control start flag=1) in step S19, andthen the processing flow proceeds to step S20. In step S20, it isdetermined whether or not the blade 2 a reaches the deceleration startposition X in the backward wiping stroke. When the blade 2 a does notreach the deceleration start position X in step S20, the processing flowproceeds to steps S14 to S17, where the feedback control is continued.On the other hand, when the blade 2 a reaches the deceleration startposition X in step S20, the processing flow proceeds to step S21, wherean FF control output D_(ff) is calculated.

Here, the motor rotation number calculation section 28 sets the PWM dutybased on the following expression (expression (3)).FF control output D _(ff) =PWM duty (ffc sta duty) at FF control startposition×Ksd  expression (3)(Ksd=current target speed tgt spd/target speed pek tgt spd atdeceleration start point)

As described above, Ksd is a control coefficient indicating a decrementin an output from the deceleration start point. FIG. 9 is an explanatoryview illustrating concepts of the FF control start position P, andcurrent target speed tgt spd and target speed pek tgt spd at thedeceleration start point in the present invention. As illustrated inFIG. 9, the target speed pek tgt spd at the deceleration start point isreduced in a predetermined parabolic curve after the deceleration startposition, and the curve itself goes up and down (duty value increases ordecreases) according to the duty value at the deceleration start point.

After calculation of the FF control output D_(ff) in step S21, theprocessing flow proceeds to step S22. In step S22, according to the sameprocedure as that of the steps S14 to S17, the control duty value D_(fb)in the feedback control (Dfb=above-mentioned D2) is calculated. Then, instep S23, based on the above values (D_(ff), D_(fb)) and the followingexpression (4), the PWM duty value is set/output.Output PWM duty=(a×D _(ff) b×D _(fb))/c  expression (4)(where, c=a+b)

As described above, in the control processing in the third embodiment,both the FF control value D_(ff) (specified value) assuming disturbanceand feedback calculation value D_(fb) are used for determination of thePWM duty value, and weighting of the values D_(ff) and D_(fb) isappropriately adjusted. Consequently, as above, it is possible to reducedisturbance in the Duty or motor rotation number due to the load changewhile coping with the abrupt change in the glass surface state. Thus,adaptability to the disturbance is improved to allow the wiping movementto be further stabilized. In the third embodiment, as in the firstembodiment, it is possible to perform the above control by using onlythe FF control output D_(ff) without performing the feedback operation(control duty value D_(fb) is not used: b=0).

The present invention is not limited to the above embodiments, but maybe variously modified without departing from the spirit of the presentinvention.

For example, in the above first embodiment, the PI feedback control isnot performed after the deceleration start position X; however, theevent described in the second embodiment can be assumed, so that the PIfeedback control may be continuously calculated after the decelerationstart position X and, when the current blade speed deviates from thetarget speed by a predetermined value or more (e.g., 20% or more), thecontrol mode may be switched from the control according to the specifiedvalue D1 to PI feedback control.

Further, the values a and b in the second and third embodiments are justillustrative, and may be appropriately changed according to a vehicletype or disturbance to be assumed. For example, it is possible to placeimportance on the control according to the specified value D1 by settingthe values of a and b to 2 and 1, respectively; conversely, it ispossible to place importance on the control according to the feedbackcalculation value D2 by setting the values of a and b to 1 and 2,respectively. Further, the weighting of the D1 and D2 may be changed asneeded depending on the disturbance state, or the D1 and D2 may bechanged as needed by learning.

Further, in the above respective embodiments, the ratio between thecurrent target speed tgt spd and target speed pek tgt spd at thedeceleration start point is used as the deceleration coefficient Ksd.Alternatively, however, in a wiper device that performs motor control bypreviously setting a target duty value corresponding to the bladeposition, a ratio (current target duty value/target duty value atdeceleration start point) between the target duty value at the currentposition and target duty value at the deceleration start position may beused as the Ksd.

In addition, although a control example in the backward wiping strokehas been described in the above respective embodiments, the control modeaccording to the present invention can be applied to the forward wipingstroke. As described above, also in the forward wiping stroke, the samephenomenon as that in the backward wiping stroke may occur. Thus, inorder to prevent the unstable phenomenon in the forward wiping stroke,the duty calculation method may be changed from the deceleration startpoint of the wiper system also in the forward wiping stroke, as in thebackward wiping stroke. That is, the present invention can be carriedout in the motor deceleration regions set in the respective forward andbackward wiping strokes constituting one control cycle. Thus, accordingto the present invention, after the deceleration start position, themotor speed control can be performed under a predetermined control modeset according to the duty value at the deceleration start position or FFcontrol start position, that is, the load in the maximum speed range.The one control cycle in the present invention is a control cyclerelated to one reciprocating operation of the wiper blade.

Further, in the above respective embodiments, the two motors are used todrive the respective wiper arms in the wiper system as illustrated inFIG. 1; however, the wiper system to which the present invention can beapplied is not limited to this. For example, the present invention canbe applied to a wiper system that uses a link mechanism to move twowiper arms with one electric motor.

Further, although the electric motor illustrated in FIG. 2 has onesensor magnet 31 and one rotary encoder IC 32, a configuration of theelectric motor is not limited to this. For example, it is possible touse a motor having a sensor magnet mounted to the rotary shaft andhaving a hall IC disposed so as to face the sensor magnet for thepurpose of sensing a pole change in the sensor magnet. This motor is apulse specification for detecting a pulse and outputs a pulse from thehall IC with rotation of the motor. The number of the hall ICs providedin the motor is not limited.

REFERENCE SIGNS LIST

-   1 a, 1 b: Wiper arm-   2 a, 2 b: Wiper blade-   3: Windshield-   4 a: Wiper shaft-   5: Wiping range-   6 a, 6 b: Electric motor-   7: Motor body-   8: Deceleration mechanism-   10: Wiper control device-   11: ECU-   12: On-vehicle LAN-   13: Communication line-   21: CPU-   22: Data transmission/reception section-   23: ROM-   24: RAM-   25: Position detection section-   26: Blade speed detection section-   27: Blade speed determination section-   28: Motor rotation number calculation section-   29: Drive control instruction section-   31: Sensor magnet-   32: Rotary encoder IC-   33: Rotor-   34: Rotary shaft-   35: Worm-   36: Worm wheel-   A: Lower inversion position-   B: Upper inversion position-   X: Deceleration start position-   Ksd: Deceleration coefficient-   tgt spd: Current blade target speed-   pek tgt spd: Blade target speed at deceleration start point-   ffc sta duty: PWM duty at FF control start position-   D_(ff): FF control output (duty value)-   D_(fb): Control duty value in feedback control

The invention claimed is:
 1. A wiper control method for a wiper device,the wiper device including a wiper blade disposed on a surface and anelectric motor for reciprocating the wiper blade on the surface, theelectric motor being subjected to pulse width modulation (PWM) dutycontrol based on a target speed of the wiper blade set according to aposition of the wiper blade on the surface, the wiper control methodcomprising: after a deceleration start position is reached at which aspeed of the wiper blade is made to start being reduced in a wipingoperation of the wiper blade, driving the electric motor using an outputPWM duty value, the output PWM duty value being obtained by multiplyinga PWM duty value at a feedforward control start position set before thedeceleration start position by a deceleration coefficient, wherein theoutput PWM duty value fluctuates according to a load state in a regionover which the wiper blade on the surface is operating at a maximumspeed, and the deceleration coefficient used is based on the position ofthe wiper blade on the surface and is a ratio between a target speed atthe deceleration start point and a target speed according to theposition of the wiper blade.
 2. The wiper control method according toclaim 1, further comprising: feedback-controlling the electric motorbased on the speed of the wiper blade; and after the deceleration startposition, controlling the electric motor using only the value obtainedby multiplying the PWM duty value at the feedforward control startposition by the deceleration coefficient.
 3. The wiper control methodaccording to claim 1, further comprising: after the deceleration startposition, controlling the electric motor under coefficient control usingthe value obtained by multiplying the PWM duty value at the feedforwardcontrol start position by the deceleration coefficient; andfeedback-controlling the electric motor in place of the coefficientcontrol when the speed of the wiper blade deviates from the target speedby a predetermined value or more.
 4. The wiper control method accordingto claim 1, further comprising: feedback-controlling the electric motorbased on the speed of the wiper blade; and after the deceleration startposition, controlling the electric motor by a combination of thefeedback control and control using the value obtained by multiplying thePWM duty value at the feedforward control start position by thedeceleration coefficient.
 5. The wiper control method according to claim4, wherein after the deceleration start position, the electric motor isdriven by the PWM duty value calculated as follows:output PWM duty=(a×D1+b×D2)/c(where, c=a+b) using a PWM duty value D1 obtained by multiplying the PWMduty value at the feedforward control start position by the decelerationcoefficient and a PWM duty value D2 based on the feedback control.
 6. Acontrol device for a wiper device, the wiper device including a wiperblade disposed on a surface and an electric motor for reciprocating thewiper blade on the surface, the wiper device having, in one controlcycle of the wiper blade, a deceleration region over which the electricmotor is decelerated, the electric motor being subjected to pulse widthmodulation (PWM) duty control based on a target speed of the wiper bladeset according to a position of the wiper blade on the surface, thecontrol device comprising: a non-transitory medium storing a program;and a hardware processor that executes the program, the execution of theprogram causing the control device to operate as: a blade positiondetection section that detects a current position of the wiper blade; ablade speed detection section that detects a current moving speed of thewiper blade; a blade speed determination section that compares a bladetarget speed corresponding to the current position of the wiper bladeand the current speed of the wiper blade; a motor rotation numbercalculation section that calculates a rotation number of the electricmotor based on a result of the determination made by the blade speeddetermination section; and a drive control instruction section thatcontrols operation of the electric motor based on an instruction fromthe motor rotation number calculation section, wherein after adeceleration start position is reached at which a speed of the wiperblade is made to start being reduced in a wiping operation of the wiperblade, the motor rotation number calculation section uses an output PWMduty value for driving the electric motor, the output PWM duty valuebeing obtained by multiplying a PWM duty value at a feedforward controlstart position set before the deceleration start position by adeceleration coefficient, the output PWM duty value fluctuates accordingto a load state in a region over which the wiper blade on the surface isoperating at a maximum speed, and the deceleration coefficient used isbased on the position of the wiper blade on the surface and is a ratiobetween a target speed at the deceleration start point and a targetspeed according to the position of the wiper blade.
 7. The wiper controldevice according to claim 6, wherein the electric motor isfeedback-controlled by the motor rotation number calculation sectionbased on the speed of the wiper blade and is, after the decelerationstart position, driven using only the value obtained by multiplying thePWM duty value at the feedforward control start position set before thedeceleration start position by the deceleration coefficient.
 8. Thewiper control device according to claim 6, wherein after thedeceleration start position, the electric motor is driven undercoefficient control using the value obtained by multiplying the PWM dutyvalue at the feedforward control start position set before thedeceleration start position by the deceleration coefficient and isdriven under the feedback control in place of the coefficient controlwhen the speed of the wiper blade deviates from the target speed by apredetermined value or more.
 9. The wiper control device according toclaim 6, wherein the electric motor is feedback-controlled by the motorrotation number calculation section based on the speed of the wiperblade and is, after the deceleration start position, driven bycombination of the feedback control and control using the value obtainedby multiplying the PWM duty value at the feedforward control startposition set before the deceleration start position by the decelerationcoefficient.
 10. The wiper control device according to claim 9, whereinafter the deceleration start position, the electric motor is driven bythe motor rotation number calculation section using the PWM duty valuecalculated as follows:output PWM duty=(a×D1+b×D2)/c(where, c=a+b) using a value D1 obtained by multiplying the PWM dutyvalue at the feedforward control start position set before thedeceleration start position by the deceleration coefficient and a PWMduty value D2 based on the feedback control.